1. Field of the Invention
The present invention relates to a V-type internal combustion engine mounted in a vehicle such as a motorcycle and, particularly relates to the engines cylinder block structure.
2. Description of Background Art
A vehicular V-type internal combustion engine wherein a front cylinder part arranged on the front side in a vehicular travel direction and a rear cylinder part arranged on the rear side in the vehicular travel direction are arranged so that they form an approximate V shape is known in Japanese published examined patent application Ser. No. H3-18052 for example and others. In such a V-type internal combustion engine, the respective center lines of front and rear cylinder holes, respectively, provided to the front cylinder part and the rear cylinder part are displaced from a central position between a pair of journal walls adjacent in the axial direction of a crankshaft.
To avoid interference with an accessory such as a radiator in the case wherein a V-type internal combustion engine is mounted in a vehicle such as a motorcycle, it is desirable that the front cylinder part is tilted so that the upper end is as low as possible. However, when the front cylinder part is greatly tilted on the front side, the lower end of the front cylinder hole provided in the front cylinder part is close to the journal wall provided in the lower part of a cylinder block and in the case where the inner surface of the front cylinder hole is honed, the journal wall interferes with a honing machine. Therefore, in the above conventional type, the tilt angle to the front side of the front cylinder part cannot be set so that it is large and the positions of the respective upper ends of the front cylinder part and the rear cylinder part are set so that they are approximately equal in height. To avoid interference between the journal wall and the honing machine, the distance between the journal walls adjacent in the axial direction of the crankshaft can be also set to a large value, however, in that case, the cylinder block, that is, the internal combustion engine is a large-size.